Is there a custom renderType/userFunc for plugins?

Is there a method/way to render a custom backend element?

What I’m looking for is a way to, within a plugin, skip FlexForms and freely render custom HTML in the backend.

I have found that it’s possible to render HTML on any of the tabs using a combination of

  • ‘renderType’ => ‘specialField’,
  • addTCAcolumns
  • addToAllTCAtypes

I, however, need this renderType call to happen when selecting a plugin while adding a content element.
Can this be accomplished at all in Typo3 or are FlexForms the only method of rendering backend plugin configuration UI’s?

FlexForms are not the only method of rendering. As you answered yourself you can create an own field where you can use the HTML you want for your form field.